The invention relates to a method, and to an arrangement for the application of the method, for the identification of rolls, in particular, big paper rolls, by means of a code attached to or marked on the end surface of the roll, which code comprises several code characters located side by side.
Big paper rolls are produced in a paper mill for different deliveries comprising rolls of different axial length, different diameter and/or different weight. Rolls being similar with respect to the properties just mentioned may comprise different paper grades having different density and/or composition. Also the package requirement may vary, for instance, shipping of rolls to overseas customers requires a much more durable package than rolls delivered to nearby customers. In order to avoid delivery delays it is also important to be able to reproduce a roll of a specific character quickly, if the original roll winding has failed or if the roll has been damaged.
In an automatized paper roll production and packaging line, for instance, the roll weight and diameter are measured and the measured values are transferred to the governing and data processing unit of the line. A labelling unit produces an identification label for each roll and attaches it to the end surface of the roll. The label indicates the measured values and possibly also other recorded data identifying the customer and the paper grade of the roll. All data are expressed in the form of a code modified to suit an automatic reader device.
It is suitable to use a so-called bar code formed by a series of stripes. The code is read across the stripes by sensing the value of the code stripes one after another. In order to facilitate the code reading, the label is usually attached to the center of the roll. Nevertheless, there will be variations in the vertical position of the label, because the roll diameters may vary considerably. Another problem is that the scanning plane of the reader has no connection with the random orientation of the label. It is known to eliminate this problem by rotating the roll during code reading by means of scanning all over the roll end surface by means of a narrow, collimated optical beam. Thus, the scanning motion of the beam has to cover the entire end surface of the roll. This is cumbersome, time-consuming and uneconomical. Moreover, roll rotation requires rotation means, which increases the expenses. Rotation of a roll weighing several tons is slow, and slows down the entire roll handling process.